Harvesting Energy in the Sky

withoutfeathers writes "The Economist magazine has an article on Flying wind farms. Mind you, we're not talking about ordinary, terrestrial windmills here. We're talking about actual airborne — up to 10km in the sky — wind farms intended to harvest the immense supply of energy in the jet stream. On the surface, the idea seems a little eccentric but, in fact, San Diego (California, US) based Sky WindPower has, apparently, thought their concept through pretty thoroughly and believes they can not only make this work, but do so profitably. The article discusses several other ideas for high-flying wind farming including a Dutch proposal to use pairs of kites to drive a generator."

Are they serious?

[Anonymous Coward]

This is a terrible idea. Harnessing wind down by the ground is local, but sucking energy out of the jet stream will cause problems "down stream". Operate a sizable "facility", sit back, and watch the "unintended side effects" proliferate.

Granted, I didn't RTFA. :D

Great

[demonbug]

Hey, lets put a bunch of aircraft up at 10km, with cables that tie them to the ground! Excellent idea! Why didn't anyone think of this before?

Oh, that's right - they did. They used them to prevent aircraft from flying over towns/cities/military targets (it sort of worked).

It also doesn't seem to make a whole lot of sense to stick a bunch of obstacles up in the jet stream. You know, where airliners tend to like to fly (at least when going west to east).

Oh, and doesn't the jet stream tend to be rather dynamic - as in, it's course often changes by hundreds or even thousands of miles?

Re:Are they serious?

[2short]

So don't RTFA (I haven't :) ), but make some estimate in your head of the total percent of the energy in the jet stream they could possibly harvest. I have some idea the scales involved and the efficiency of wind turbines, and in my wildest speculations I can't see how they are going to make even a tenth of a percent difference in the strenght of the stream. It's not going to be a problem.

Re:Well

[Mantis8]

What are chances that the geographical areas where these contraptions are installed get hit by bad weather (i.e. typhoons, tornados, hurricanes, hailstorms, lightning, etc)? That not only will destroy millions of dollars of power-generation equipment and disrupt power, but potentially kill people, animals, or damage crops, buildings, etc on the ground.

Assuming the power station comes down in any uncontrolled fashion, and from the heights they are talking about and the strong jet stream winds they are dealing with, the power generation station could potentially travel many miles before it hits ground, endangering a very very large area below. How would this affect the value of real estate in the same areas because of the risk? I guess the insurance industry might benefit from this if the odds are in their favor.

Global warming almost guarantees more severe storms, more often, making power generation of this sort even more risky.

It's not just disruptive in the jet stream

[BrewerDude]

The cable that is tethering it to the ground will be a hazard to aviation and all altitudes below the generator. Not only would the cable be very hard to see, but, unlike power cables and guy wires for antennas, it would also be hard to chart, since I imagine that the generator will move around quite a bit as the jetstream fluctuates.

Profit

[Haxx]

It's a good thing it might be profitable, otherwise we would have to forget about the idea forever.

Re:Hmm

[gardyloo]

With the recent stories of space junk falling to earth, could we someday be troubled by power stations falling on us?

SOMEday?!? I'm troubled now.

Re:Would this cause any problems with the jet stre

[Anonymous Coward]

But fractions of percents are all we're discussing with regard to global warming, too...

Re:Are they serious?

[KillerCow]

This is a terrible idea. Harnessing wind down by the ground is local, but sucking energy out of the jet stream will cause problems "down stream". Operate a sizable "facility", sit back, and watch the "unintended side effects" proliferate.

You're right. We should stick to burning coal, firing gas, building dams, and fissioning radioactive materials. Those have all proven to have no unintended consequences.

Re:Would this cause any problems with the jet stre

[CorSci81]

I'd honestly be more concerned with global warming killing the jet stream than this. The jet stream is largely the result of low-altitude/surface-level thermal gradients (ie the equator to pole temperature difference). Given that most climate models predict the poles will warm significantly more than the equator, if they turn out to be correct I'd say that's far more troubling to the jet stream than a few big kites.

Re:It's not just disruptive in the jet stream

[MasaMuneCyrus]

There already exist no-fly zones all over the place. I don't see why we couldn't just set up a perimeter around the cable as a no-fly zone and planes fly around it, like they would a military base, an erupting volcano, or other such places.

Re:It's not just disruptive in the jet stream

[quenda]

but, unlike power cables and guy wires for antennas, it would also be hard to chart, since I imagine that the generator will move around quite a bit as the jetstream fluctuates.

Why not just copy the antennas, and use three guy wires? Stability, and safety.

These things are gyrocopter kites

[Engineer-Poet]

Falling to the ground is rather unlikely. If the unit can still be controlled, the best scenario is to just let it autorotate down and lay its cable down gently as it goes.

Re:Hmm

[Tdawgless]

http://en.wikipedia.org/wiki/Wind_resistance [wikipedia.org]

"Uncontrolled?"

[Ungrounded Lightning]

What are chances that the geographical areas where these contraptions are installed get hit by bad weather (i.e. typhoons, tornados, hurricanes, hailstorms, lightning, etc)?

They're in the jet stream. That's up at the TOP of the troposphere. The turbulent violence you're talking about happens further down - the top mostly just has winds, and the jet stream is already the worst of it.

Assuming the power station comes down in any uncontrolled fashion, and from the heights they are talking about and the strong jet stream winds they are dealing with, the power generation station could potentially travel many miles before it hits ground, endangering a very very large area below.

Now that would depend on the type of elevated structure. But most of them have acceptable failure mechanisms.

For instance: The four-bladed "helicopter" should auto-gyro nicely. If it loses its tether the blades keep spinning and keep providing lift - in the correct direction even. By transferring power from one blade to another as needed you can navigate it like a glider - even upwind, trading altitude for blade momentum as you drop. This lets you fly it to a landing area, landing vertically and quite gently, even without any additional power source onboard. Or find an updraft and soar until any crummy weather at ground level has moved on.

Balloons

[Anonymous Coward]

Why couldn't balloons be used to hold the weight of the tether AND the generators? This way, power isn't being wasted in keeping everything up there.

Re:In the Jet Stream...

[ultranova]

I'd also say that the energy cost of raising a 10km insulated power cable into the air would also need to be resolved too.

Why would the cable need to be insulated ? Use alternating power through a bare steel wire, and just shield the transformers at each end so they won't get fried if lightning strikes. That way you don't need multiple wires and can use the tether itself as the power cable, allowing you to use very high voltages to minimize power losses.